(1) Field of the Invention
The present invention relates, in general, to spray coating apparatus and more particularly to spray coating apparatus for rotating a workpiece relative to a spray station to obtain uniform spray coating of the workpiece.
This spray coating apparatus is designed for adaption to an automated spray station in an assembly line.
(2) Description of the Prior Art
Heretofore, spray coating devices have been proposed for spray coating of workpieces, such as shoes, wherein the workpiece was mounted for rotation in the horizontal plane about a vertical axis relative to a spray station so as to coat the workpiece uniformly on all sides facing the spray station. Such a spray coating apparatus is disclosed in U.S. Pat. No. 3,390,660 issued July 2, 1968.
It is also known from the prior art to place a reusable surface insulation tile on a fixed pedestal and to spray the tile by moving the spray gun relative to the stationary horizontal tile. Alternatively, it is known from the prior art to mount the tile to a model holding device and, while holding the tile on the model holding device in one hand, spraying the tile with the other hand. Reusable surface insulation tiles are disclosed in U.S. Pat. No. 3,952,083 issued Apr. 20, 1976.
A 1/4" strip along the bottom of each vertical side edge of the tile must be coating free. Therefore, masking tape was applied to that area before spraying. This masking tape was removed after the coating was dried but before the coating was glazed.
In the prior art method wherein the tile rested in the horizontal plane on the pedestal for spray coating, the sides of the tile were vertical and the top of the tile was horizontal. A uniform coating of a specified thickness was difficult to achieve with this arrangement because the coating slurries were of relatively low viscosity and often ran on the tile's vertical sides while the coating deposited on the top of the tile was much thicker than on its sides.
When a hand-held holder was employed, it was cumbersome to use and increased the possibility of handling damage to the coating. Neither of the prior art methods were amenable to large scale manufacturing of reusable insulation tile. In addition, the use of the masking tape to obtain an uncoated border along the bottom of the vertical sides of the tile was time consuming and when the masking tape was removed, the unfired coating was often damaged.